The spelling of "culpabl" is actually incorrect, as the correct spelling is "culpable." The IPA phonetic transcription of "culpable" is /ˈkʌlpəbəl/, which breaks down to "KUL-puh-buhl." The first syllable is pronounced with an "uh" sound and the "l" is lightly pronounced. The second syllable has a short "u" sound followed by the "p" and "b" consonants, and the final syllable is pronounced with a schwa sound and a soft "l." Remembering the correct spelling of words can be aided by practicing their phonetic transcription.
There seems to be a typographical error in your question. The correct word you are referring to is likely "culpable". The etymology of the word "culpable" is derived from the Latin word "culpabilis", which means "worthy of blame" or "guilty". It is formed from the Latin root "culpa", meaning "fault" or "blame". The word "culpable" entered Middle English from Old French around the 14th century.